There is another easy to do exploit/hack/glitch in BL2 out, and this time it allows you to get unlimited Eridium as long as you are on a certain mission.  Here is how to do the glitch step by step.

1. When you are in Three Horns Valley, first go to the hideout where you fight the Bad Maw end quest boss. Kill him, and pick up the Eridium he drops.
2. After killing Bad Maw, enter the Bloodshot Stronghold, and choose the “Save and Quit” option..
3. Now you can resume/continue the game, return to Three Horns Valley and slay Bad Maw again to get more Eridium.
4. You can keep doing this over and over to get unlimited Eridium.

Enjoy! Remember this is an exploit and it can take some fun away from the game, so just know that before you use it!